In power electronics and electrical engineering, control concepts in which sinusoidal alternating variables—or alternating variables which are assumed to be largely sinusoidal—such as voltages or currents cannot be controlled directly in respect of their instantaneous time value but rather in respect of an instantaneous value which is corrected by the phase angle within the periods, in summary called field-oriented or vector control. To this end, the detected alternating variables are each transferred into a coordinate system which rotates at the frequency of the alternating variables. Identical variables, to which all customary methods of control engineering can be related, are then produced from the alternating variables within this rotating coordinate system.
For practical reasons, a Cartesian coordinate system comprising two axes d and q which are perpendicular to one another is generally selected, in particular for field-oriented control of synchronous machines. Therefore, the actuation signals for a three-phase four-quadrant actuator are formed by way of space vector modulation (space vector pulse width modulation, SVPWM) on the basis of suitable reference values for the corresponding current components.
In order to achieve a required torque, different combinations of the two phase currents id and iq generally come into consideration. In this case, that combination with the lowest phase current and therefore maximum torque per ampere (MTPA) is often selected in practice. In this way, the copper losses of the machine which occur primarily in the stator should be largely minimized.
CN104319969, which is incorporated by reference herein, and US2013207589, which is incorporated by reference herein, disclose control methods for an electrical machine, in particular a permanent-magnet synchronous machine for electric and hybrid vehicles, in which methods the currents id and iq are analyzed and eddy current and hysteresis losses are minimized.
DE102010050344, which is incorporated by reference herein, discloses a control method for an electrical machine in which iron losses are generally calculated.
US2005073280, which is incorporated by reference herein, US2013006593, which is incorporated by reference herein, US2013119900, which is incorporated by reference herein, WO04073156, which is incorporated by reference herein, US2016028343, which is incorporated by reference herein, and U.S. Pat. No. 6,605,912, which is incorporated by reference herein, disclose further control methods in which magnetic noise is partially reduced and the torque ripple is compensated for.